Neuroendocrine differentiation in castration resistant prostate cancer. Nuclear medicine radiopharmaceuticals and imaging techniques: A narrative review

Incidence of dural metastases in castrate-resistant prostate cancer

Purpose:

The natural history and clinical manifestations of dural metastases (DM) in castrate-resistant prostate cancer (CRPC) will change with advances in new hormonal therapy. Here, we characterised the incidence, clinical presentation, and outcomes of patients with DM in a contemporary patient cohort with CRPC.

Methods:

We retrospectively reviewed our CRPC database from 2012 to 2020. The primary outcome was the diagnosis of DM, defined as metastasis to the dura mater in the brain or spine. We describe the presenting symptoms, biochemistry, radiologic findings, and therapy sequence for all DM patients. Multivariable logistic regression was performed to identify predictors of DM.

Results:

Six of the 275 patients (2.2%) with CRPC developed DM. The average age of CRPC diagnosis for patients with DM was 65.6 years. Mean patient survival was 4.5 months after the diagnosis of DM. At the time of CRPC diagnosis, patients who developed DM were significantly younger, had lower baseline haemoglobin, higher lactate dehydrogenase (LDH), and elevated alkaline phosphatase (ALP) compared to those without DM. On multivariable analysis, younger age of CRPC diagnosis was found to be a predictor for DM.

Conclusion:

The presence of neurological symptoms in the context of younger age, anaemia, and elevated baseline LDH and ALP are associated with DM in CRPC.

Level of Evidence:

4

The Triple-Tracer strategy against Metastatic PrOstate cancer (3TMPO) study protocol

OBJECTIVE

To determine the prevalence of intra-patient inter-metastatic heterogeneity based on positron emission tomography (PET)/computed tomography (CT) in patients with metastatic castration-resistant prostate cancer (mCRPC) and to determine the prevalence of neuroendocrine disease in these patients and their eligibility for radioligand therapies (RLTs).

PATIENTS AND METHODS

This multicentre observational prospective clinical study will include 100 patients with mCRPC from five Canadian academic centres. Patients with radiological or biochemical progression and harbouring at least three metastases by conventional imaging will be accrued. Intra-patient inter-metastatic heterogeneity will be determined with triple-tracer imaging using fluorine-18 fluorodeoxyglucose (¹⁸ F-FDG), gallium-68-(⁶⁸ Ga)-prostate-specific membrane antigen (PSMA)-617 and ⁶⁸ Ga-DOTATATE, which are a glucose analogue, a PSMA receptor ligand and a somatostatin receptor ligand, respectively. The ⁶⁸ Ga-PSMA-617 and ¹⁸ F-FDG PET/CT scans will be performed first. If at least one PSMA-negative/FDG-positive lesion is observed, an additional PET/CT scan with ⁶⁸ Ga-DOTATATE will be performed. The tracer uptake of individual lesions will be assessed for each PET tracer and patients with lesions presenting discordant uptake profiles will be considered as having inter-metastatic heterogeneous disease and may be offered a biopsy.

EXPECTED RESULTS

The proposed triple-tracer approach will allow whole-body mCRPC characterisation, investigating the inter-metastatic heterogeneity in order to better understand the phenotypic plasticity of prostate cancer, including the neuroendocrine transdifferentiation that occurs during mCRPC progression. Based on ⁶⁸ Ga-PSMA-617 or ⁶⁸ Ga-DOTATATE PET positivity, the potential eligibility of patients for PSMA and DOTATATE-based RLT will be assessed. Non-invasive whole-body determination of mCRPC heterogeneity and transdifferentiation is highly innovative and might establish the basis for new therapeutic strategies. Comparison of molecular imaging findings with biopsies will also link metastasis biology to radiomic features.

CONCLUSION

This study will add novel, biologically relevant dimensions to molecular imaging: the non-invasive detection of inter-metastatic heterogeneity and transdifferentiation to neuroendocrine prostate cancer by using a multi-tracer PET/CT strategy to further personalise the care of patients with mCRPC.

Prostate Cancer With Neuroendocrine Differentiation Recurring After Treatment With 177Lu-PSMA: A Chance for 177Lu-DOTATATE Therapy?

ABSTRACT

Prostate cancer with NED (neuroendocrine differentiation) may occur in various stages of the disease, which is associated with a poor prognosis and treatment resistance. We present a case of a patient with metastatic castration-resistant prostatic cancer, who was treated with 7 cycles of 177Lu-PSMA and a very good response. Although only few foci with PSMA uptake were remained in the last posttreatment images, PSA levels dramatically began to rise. This raised suspicion for NED, and 68Ga-DOTATATE was done showing sufficient uptake to consider a trial of 177Lu-DOTATATE. The patient reported pain response, and PSA levels dropped after 1 cycle of the treatment.

The prognostic significance of neuroendocrine markers and somatostatin receptor 2 in hepatocellular carcinoma

Prostatic and colon carcinomas with neuroendocrine differentiation are reported to behave more aggressively than those without such differentiation. In hepatocellular carcinomas (HCCs), however, only a few studies have reported the expression status of neuroendocrine markers and somatostatin receptor 2, the main target of a somatostatin analog. Furthermore, the prognostic significance of the markers in HCCs has not been fully explored. We evaluated the expression of the neuroendocrine makers (chromogranin A, synaptophysin, and CD56) and somatostatin receptor 2 (SSTR2) in 95 HCCs, and investigated the correlation between the expression of these markers and clinicopathological findings. Chromogranin A was immunolocalized in 2 cases, synaptophysin in 15 cases, CD56 in 11 cases, and SSTR2 in 19 cases. Immunoreactivity of synaptophysin and CD56 were the significant unfavorable prognostic factors in terms of 2-year disease-free survival (DFS) and the overall survival (OS) along with a high nuclear mitosis level (>10/10 high-power field), a larger tumor size (>5 cm), the presence of vascular and/or biliary invasion, and high TNM stage (III/IV). Multivariate Cox proportional hazards analysis identified synaptophysin as an independent prognostic factor for 2-year DFS and OS. Synaptophysin expression can be used to predict an unfavorable prognosis in patients with HCC.

Unravelling the molecular mechanisms of prostate cancer evolution from genotype to phenotype

Prostate cancer (PC) is the most frequently diagnosed cancer and the second leading cause of cancer-related death in men in the Western society. Unfortunately, although the vast majority of patients are initially responsive to androgen-deprivation therapy (ADT), most cases eventually develop from hormone-sensitive prostate cancer (HSPC) to castration-resistant prostate cancer (CRPC). The main reason is PC heterogeneity and evolution during therapy. PC evolution is a continuously progressive process with combination of genomic alterations including canonical AR, TMPRSS2-ERG fusion, SPOP/FOXA1, TP53/RB1/PTEN, BRCA2. Meanwhile, signaling pathways including PI3K, WNT/β-catenin, SRC, IL-6/STAT3 are activated, to promote epithelial mesenchymal transition (EMT), cancer stem cell (CSC)-like features/stemness and neuroendocrine differentiation (NED) of PC. These improve our understanding of the genotype-phenotype relationships. The identification of canonical genetic alterations and signaling pathway activation in PC has shed more insight into genetic background, molecular subtype and disease landscape of PC evolution, resulting in a more flexible role of individual therapies targeting diverse genotype and phenotype presentation.

Undesirable Status of Prostate Cancer Cells after Intensive Inhibition of AR Signaling: Post-AR Era of CRPC Treatment

Recent advances in prostate cancer (PC) research unveiled real androgen receptor (AR) functions in castration-resistant PC (CRPC). Moreover, AR still accelerates PC cell proliferation via the activation of several mechanisms (e.g., mutation, variants, and amplifications in CRPC). New-generation AR signaling-targeted agents, inhibiting extremely the activity of AR, were developed based on these incontrovertible mechanisms of AR-induced CRPC progression. However, long-term administration of AR signaling-targeted agents subsequently induces the major problem that AR (complete)-independent CRPC cells present neither AR nor prostate-specific antigen, including neuroendocrine differentiation as a subtype of AR-independent CRPC. Moreover, there are few treatments effective for AR-independent CRPC with solid evidence. This study focuses on the transformation mechanisms of AR-independent from AR-dependent CRPC cells and potential treatment strategy for AR-independent CRPC and discusses them based on a review of basic and clinical literature.

New Frontiers in Molecular Imaging Using Peptide-Based Radiopharmaceuticals for Prostate Cancer

The high incidence of prostate cancer (PCa) increases the need for progress in its diagnosis, staging, and precise treatment. The overexpression of tumor-specific receptors for peptides in human cancer cells, such as gastrin-releasing peptide receptor, natriuretic peptide receptor, and somatostatin receptor, has indicated the ideal molecular basis for targeted imaging and therapy. Targeting these receptors using radiolabeled peptides and analogs have been an essential topic on the current forefront of PCa studies. Radiolabeled peptides have been used to target receptors for molecular imaging in human PCa with high affinity and specificity. The radiolabeled peptides enable optimal quick elimination from blood and normal tissues, producing high contrast for positron emission computed tomography and single-photon emission computed tomography imaging with high tumor-to-normal tissue uptake ratios. Owing to their successful application in visualization, peptide derivatives with therapeutic radionuclides for peptide receptor radionuclide therapy in PCa have been explored in recent years. These developments offer the promise of personalized, molecular medicine for individual patients. Hence, we review the preclinical and clinical literature in the past 20 years and focus on the newer developments of peptide-based radiopharmaceuticals for the imaging and therapy of PCa.

177Lu-PSMA and 177Lu-DOTATATE Therapy in a Patient With Metastatic Castration-Resistant Prostate Cancer and Neuroendocrine Differentiation

We presented a promising result of radionuclide therapy using Lu-PSMA and Lu-DOTATATE in a patient with prostatic adenocarcinoma and neuroendocrine differentiation. Functional imaging of somatostatin receptors in patients with metastatic castration-resistant prostate cancer may pave the way toward implementation of novel radionuclide targets for the treatment of this aggressive subtype of prostate cancer.